BOCA RATON, Fla. – President Barack Obama sharply challenged Mitt Romney on foreign policy in their final campaign debate Monday night, saying, “Every time you’ve offered an opinion you’ve been wrong.” The Republican coolly responded, “Attacking me is not an agenda” for dealing with a dangerous world.

Romney took the offensive, too. When Obama said the U.S. and its allies have imposed crippling sanctions on Iran to halt nuclear weapons development, the Republican challenger responded that the U.S. should have done more. He declared repeatedly, “We’re four years closer to a nuclear Iran.”

Despite the debate’s stated focus on foreign affairs, time after time the rivals turned the discussion back to the slowly recovering U.S. economy, which polls show is the No. 1 issue for most voters.